Estimated number of leprosy cases in the world.

World leprosy estimates are discussed and generated for 1991. In an effort to identify 5.5 million registered leprosy cases in the world for 1991 it was found that there also are 2-3 million people with deformities due to leprosy. The rehabilitative requirements of this population need to be served in addition to the continued multidrug therapy (MDT) needed to control prevalence. Successful leprosy control has led to a reduction from prior estimates of 10-12 million cases. There are many problems in estimating because of the low frequency of occurrence and its uneven distribution. Well-planned sample surveys are practical and cost effective only in limited areas, rather than for countries as a whole, and also include nonsampling errors. Multimethods were used to derive the world estimates, and the estimates have been adequate for planning purposes. The magnitude of the problem was addressed in 1966 by the WHO which reported 10,786,000 cases which remained stable through 1972. A 1983 estimate by the WHO Study Group on Epidemiology of Leprosy in Relation to Control was 11,525,000 cases. 95% of registered cases are from 25 countries, of which 5 countries contribute 82% (Nigeria, Brazil, Myanmar, Indonesia, and Bangladesh). The current estimates focused on these countries. In the 5 countries, not only were correction factors applied to registered cases, but intensive reviews of all available information and discussions with relevant program managers were conducted. Correction factors for each region were used unless more reliable information was available. The correction factor was calculated as the ratio of registered cases in the top 25 countries in the region to earlier country estimates. There were 5 reasons why estimates in 1991 were significantly lower: 1) cases cured through MDT, 2) removal of cases not fitting the WHO definition which requires a case to be someone receiving MDT treatment or needing treatment, 3) late effects of an intensive dapsone-based control effort, 4) strengthened control activities, and 5) natural declining trends. The patients needing rehabilitation were estimated by considering the past case records over 50 years and the proportion with deformities, the survival rate of those deformed, and the nature of control activity. Estimates and registration of cases is given for 25 countries.